In the past, functional material patterning has been done using photolithography techniques. Because this method has drawbacks, such as high costs and complicated processes, recently, functional material patterning using a dispensing apparatus, which is convenient, and makes cost cutting possible, has been under study. A method, which uses an ink jet printing apparatus, has been studied in particular.
For example, the manufacture of color filters for use with liquid crystal displays can be raised as an example of micro-patterning using an ink jet printing apparatus. This is a manufacturing method, which appropriately ejects either dyed or pigmented ink of red, blue, and green in accordance with a printing apparatus having nozzles, which eject ink of three colors, red, blue and green, producing a color filter. The ink used in this manufacturing method is ordinarily water-soluble polar ink. In most cases, water-soluble ink such as this contains glycerin or some other solvent to prevent nozzle clog when the ink dries.
Further, a method for making a luminescent material such as an organic fluorescent material, for example, into an ink, supplying this ink via dispensing onto a substrate using an ink jet method, and patterning the luminescent material is being used, and a color display device, and more particularly, an organic EL display device, which uses an organic luminescent material as a luminescent material, of a construction, in which a layer of this luminescent material is interposed between the positive and negative electrodes, is being developed.
The manufacture of this color display device (organic EL display device) is, for example, carried out as follows.
Firstly, a fluorescent material is dissolved in a suitable solvent, and made into ink. This ink (composition) is dispensed or ejected onto a transparent electrode-equipped substrate, which serves as the positive electrode of an organic EL display device, so as to cover these transparent electrodes. At this point, an electrode is either formed on a single plane, or has a strip- or mosaic-shaped pattern, and is a structure, which is connected to, and can be driven by a power source. Next, after forming a luminescent material layer by drying and removing the solvent in the ink, a small, work function metal, for example, a silver, lithium, calcium, aluminum or other metal is expediently deposited on this luminescent material layer using a vapor deposition or sputtering method, forming a negative electrode. In this fashion, a display device of a structure in which this luminescent material layer is interposed between a positive and a negative electrode is achieved.
A pattern forming method using a conventional ink jet printing technique such as this has extremely outstanding characteristics, such as saving labor, saving resources, and not requiring mask making, but it also has the drawback of limiting the materials used in the composition (dispensing composition).
In the ink jet method, a solvent such as, for example, ethanol or water is used as the solvent in the dispensing composition. However, among non-polar, or weakly polar functional materials, or polymer functional materials (luminescent materials or the like), there are those that do not dissolve in these solvents. There is also the drawback that functional materials, which either react with water and alcohol, or are decomposed by alcohol, cannot be used.
Further, in a case in which benzene, toluene, xylene or another solvent that readily dissolves a non-polar material is used as the solvent for dissolving a functional material, due to the low boiling point (high vapor pressure) of such a solvent, the drawback is that it dries easily, and is apt to cause nozzle clog. Further, either during dispensing or after dispensing, there are times in the formation of a film, when the dispensing composition is robbed of its heat of vaporization by the volatilization of the solvent, and the temperature of the dispensing composition drops, promoting the precipitation of the functional material. In addition thereto, in the case of a functional material having multiple constituents, the drawback is that phase separation occurs, the film becomes non-uniform, and the functional film is no longer able to carry out its original role.
Furthermore, in a case in which a material, which cannot be easily used, and has poor solubility like this, is used anyway, and the concentration of the dispensing composition is increased, precipitation and clogging occur. When the concentration is made weaker in an attempt to prevent clogging, the drawback is that dispensing must be performed numerous times to achieve the characteristics of the functional material, and the number of processes must be increased.
An object of the present invention is to provide a composition, which can be used in an ink jet printing method instead of a photolithography method, which is the conventional method for patterning a functional material, and can utilize a material that is either non-polar or weakly polar, or a material of a reactivity that reacts easily with water.
Further, another object of the present invention is to provide a composition, which prevents clogging at dispensing, achieves stable dispensing, and prevents precipitation of content matter during dispensing and also prevents phase separation during post-dispensing film formation. Furthermore, another object of the present invention is to provide a uniform film (functional film) manufacturing method, and a functional device (display device) such as an organic EL device, and a manufacturing method therefor.